Generally, when the skin of an individual is torn, cut or punctured (wounded), the body naturally reacts to regenerate dermal and epidermal tissue to close the wound. The wound regeneration process typically includes a set of complex biochemical events that take place in a closely orchestrated cascade to repair the damage. These events overlap in time, but may be categorized into different phases, namely the inflammatory, proliferative, and remodeling phases.
In the inflammatory phase, bacteria and debris are phagocytized and removed, and factors are released that cause the migration and division of cells involved in the proliferative phase. In the proliferative phase, the principal steps include angiogenesis, fibroplasias, granulation tissue formation, epithelialization, and wound contraction. Angiogenesis involves the development of new capillary blood vessels for the wound area to provide oxygen and nutrients to the healing tissue. In fibroplasia and granulation tissue formation, fibroblasts grow and form a new, provisional extracellular matrix (ECM) by excreting collagen and fibronectin. In epithelialization, epithelial cells crawl across the wound bed to cover the bed. In contraction, the wound is made smaller by the action of myofibroblasts, which establish a grip on the wound edges and contract themselves using a mechanism similar to that in smooth muscle cells. When the cells' roles are close to complete, unneeded cells undergo apoptosis.
It is known that a number of disease states hinder the normal wound healing process. For example, individuals with diabetes often experience problems with what are termed “diabetic foot ulcers.” Diabetic foot ulcers are sores or wounds, typically, on the feet that typically occur in individuals having diabetes. Oftentimes, these diabetic ulcers occur as a direct or indirect result of nerve damage in the feet of the individual as the prolonged high blood sugar levels associated with diabetes is linked with damage to the nerves in the feet. Such nerve damage in the feet, referred to as peripheral neuropathy, can cause loss of sensation as well as cause deformities of the feet. Due to the loss of sensation, individuals with peripheral neuropathy may hurt their feet by repetitive minor trauma (e.g., by prolonged walking) or a single major trauma (e.g., by scraping skin, stepping on objects, immersing feet in hot water, cutting toenails inappropriately, or wearing ill-fitting shoes), but nevertheless may not notice such injuries. A further complication of diabetes is a reduction in blood flow to the feet due to the arterial blockage or other causes, thereby severely inhibiting the body's ability to adequately provide complete the proliferative stage of wound regeneration/healing described above. As a result, once the skin of the foot is torn, cut, or punctured, the wound healing process (e.g., the proliferative phase) may be inordinately slow in repairing the wound. Further, once a serious wound develops, the risk of infection is high as the individual's body is simply unable to heal the wound. Even further, once an infection starts, the infection may be very difficult to reverse, and amputation of the affected limb is common.
A number of treatments have been proposed to speed wound healing in patients having diabetic ulcers. These treatments include the use of skin grafts or “tissue equivalents.” Tissue equivalents involve the isolation of replacement skin cells that are expanded and seeded onto or into a supporting structure, such as a three-dimensional bio-resorbable matrix, or within a gel-based scaffold. Both skin grafts and tissue equivalents are notably complex and, especially in the case of reduced blood flow to the patient's legs or feet, are often unsuccessful. Other treatments involve the direct application or injection at the wound site of particular pharmaceutical agent(s). Phenytoin, for example, is a drug that has been used for decades in the treatment of convulsive disorders. Recently, however, phenytoin has been investigated for its wound healing properties in the treatment of diabetic ulcers. See Bhatia, A., Prakash, S., Topical Phenytoin for Wound Healing. Dermatology Online Journal 2004; 10(1):5; and Mutyhukumarasamy M G, Sivakumar G, Manoharan G. Topical phenytoin in diabetic foot ulcers. Diabetes Care 1991; 14:909-11. Mutyhukumarasamy et al. allegedly found an improvement in the mean healing time for patients with diabetic ulcers in patients treated with phenytoin (21 days) vs. a control group (45 days). Nevertheless, the use of phenytoin for the control and healing of wounds, including diabetic ulcers, has not become a standard treatment, primarily because the incidence of amputation remains high and the degree of wound healing remains insufficient. Accordingly, there remains a need for an improved composition and method of treatment for diabetic ulcers.